Supporting Information

Transcription

1 Electronic Supplementary Material (ESI) for Polymer Chemistry. This journal is The Royal Society of Chemistry 2017 Supporting Information Photochemical Regulation of a Redox-Active Olefin Polymerization Catalyst: Controlling Polyethylene Microstructure with Visible Light Jordan M. Kaiser, W. Curtis Anderson, Jr., and Brian K. Long* University of Tennessee, Department of Chemistry, Knoxville, TN 37996, United States Long@utk.edu Contents General Methods and Materials S2 General Polymerization Procedures S2 Experimental Setup S2-S3 Results from All Tested Light Sources S3-S4 1 H and 13 C NMR Spectra S5-S9 Gel Permeation Chromatograms References S10-S17 S18 S1

2 General Methods and Materials. All reactions were performed under an inert nitrogen atmosphere using an MBraun UniLab glovebox or using standard Schlenk techniques, unless otherwise noted. All solvents were dried using an Innovative Technologies PureSolv Solvent Purification System and degassed via three freeze-pump-thaw cycles. Catalyst 1 was prepared according to literature. 1 Photoreductant 2 was purchased from Sigma Aldrich and used as received. PMAO-IP was purchased from Akzo Nobel and used as received. All other reagents were purchased from commercial vendors and used without further purification. Gel permeation chromatography (GPC) was performed at 160 C in 1,2,4-trichlorobenzene at a flow rate of 1.0 ml/min on a Malvern Viscotek HT-GPC equipped with triple detection. Quantitative 13 C NMR spectra were obtained using a Varian 500 MHz NMR and analyzed following literature procedures. 2-4 Polymer 1 H NMR spectra were obtained using a Varian 500 MHz NMR. All NMR spectra are referenced relative to their residual solvent signal. Branching content was determined by 1 H NMR spectroscopy using the formula (CH 3/3)/[(CH + CH 2 + CH 3)/2] General ethylene polymerization conditions. Under an inert atmosphere and shielded from ambient light, a Fisher-Porter bottle was charged with catalyst 1 (10 µmol), photoreductant 2 (10 μmol), toluene (150 ml), and a magnetic stir bar. The Fisher-Porter bottle was sealed, placed in a thermostated room temperature water bath (the reactor was submerged to 1/3 rd the solvent level), and covered with aluminum foil to shield from ambient light (see Figure S1). The vessel was pressurized with ethylene gas while stirring and allowed to equilibrate for 10 minutes. PMAO-IP (100 equivalents) was injected to initiate polymerization and the reaction was stirred continuously for the desired time. All polymerizations were quenched via the addition of MeOH (10 ml) and the polymer was precipitated using excess acidic MeOH (5% HCl in MeOH). The polymer was stirred in the acidic methanol for 24 hours then filtered, washed with excess methanol, and dried to constant weight in a vacuum oven. General ethylene polymerization conditions (reduced catalyst). Polymerizations requiring the reduced catalyst form were performed using the same procedure described above, except after MAO was injected, the reaction was irradiated using a Sunlite 3 W blue LED bulb for the desired amount of time. The Fisher- Porter bottles used are Lab Crest 6 oz pressure reactors (glass side-wall thickness is ~4 mm) purchased from Andrews Glass Co. The bulb was positioned 2 cm from the Fisher-Porter bottle (Figure S1a) and an aluminum foil shield was placed around the apparatus to ensure maximum irradiation while also shielding from ambient light (Figure S1b). As described above, the reactor was submerged in the water bath to 1/3 rd the solvent level to provide temperature control, yet not greatly diminish the intensity of light reaching the reaction solution. S2

3 a b Figure S1. a) Polymerization set-up. b) Polymerization set up with aluminum foil shield. Evaluation of Light Source Results. For this study, we tested three light sources: a) a 3 W blue LED, b) a 14 W compact fluorescent bulb (CFL), and c) a 36 W UV lamp. In order to identify the optimal light source, we compared their polymerization results. When comparing polymer yields (Table S1), it is clear that the UV lamp has a negative influence on catalyst productivity, and for this reason it was not used in this study. Additionally, Mark-Houwink plots were examined to analyze/compare the microstructure of the polymers produced using each different light source (Figure S2). The LED light source produced the most significant change in microstructure as compared to the CFL, which shows minimal change. For these reasons, we selected the blue LED for our in-depth study. Table S1. Comparing polyethylene yield when irradiated using various light sources. light source yield (g) Dark (no irradiation) W blue LED W UV W CFL 2.54 a Polymerization Conditions: Catalyst 1 = 10.0 mol, 2 = 10.0 mol, 150 ml of toluene, 20 C, 15 psi ethylene, 30 min polymerization, 30 min iradiation, and 100 equiv of PMAO-IP. S3

4 Intrinsic Viscosity ( ) (ml/g) 20 Dark (no irradiation) 3 W Blue LED 36 W UV Lamp 14 W CFL Mw (g/mol) Figure S2. Log-log plot of intrinsic viscosity ( ) vs M w for polyethylene produced using catalyst 1 and photoreductant 2 under irradiation by different light sources. (No light source (black), 3 W blue LED (blue), 36 W UV lamp (purple), and 14 W CFL (green)) S4

5 H 2O Figure S3. Representative 1 H NMR of polyethylene. (Table 1, Entry 2) H 2O Figure S4. Representative 1 H NMR of polyethylene. (Table 1, Entry 3) S5

6 H 2O Figure S5. Representative 1 H NMR of polypropylene. (Table 1, Entry 4) H 2O Figure S6. Representative 1 H NMR of polypropylene. (Table 1, Entry 5) S6

7 H 2O Figure S7. Representative 1 H NMR of polyethylene. (Table 1, Entry 6) H 2O Figure S8. Representative 1 H NMR of polyethylene. (Table 1, Entry 7) S7

8 H 2O Figure S9. Representative 1 H NMR of polyethylene. (Table 1, Entry 8) Figure S10. Representative 13 C NMR of polyethylene. (Table 3, exposure time = 0 min) S8

9 Figure S11. Representative 13 C NMR of polyethylene. (Table 3, exposure time = 10 min) Figure S12. Representative 13 C NMR of polyethylene. (Table 3, exposure time = 30 min) S9

10 Figure S13. GPC of polyethylene. (Table 1, Entry 2) S10

11 Figure S14. GPC of polyethylene. (Table 1, Entry 3) S11

12 Figure S15. GPC of polyethylene. (Table 1, Entry 4) S12

13 Figure S16. GPC of polyethylene. (Table 1, Entry 5) S13

14 Figure S17. GPC of polyethylene. (Table 1, Entry 6) S14

15 Figure S18. GPC of polyethylene. (Table 1, Entry 7) S15

16 Figure S19. GPC of polyethylene. (Table 1, Entry 8) S16

17 Figure S20. GPC of polyethylene. (Table 1, Entry 9) S17

18 References: 1. L. K. Johnson, C. M. Killian and M. Brookhart, J. Am. Chem. Soc., 1995, 117, P. M. Cotts, Z. Guan, E. McCord and S. McLain, Macromolecules, 2000, 33, G. B. Galland, R. F. de Souza, R. S. Mauler and F. F. Nunes, Macromolecules, 1999, 32, G. B. Galland, R. Quijada, R. Rojas, G. Bazan and Z. J. A. Komon, Macromolecules, 2002, 35, F. A. Hicks, J. C. Jenkins and M. Brookhart, Organometallics, 2003, 22, S18